This application relates to a wireline transmission circuit for preparing electronic signals to be transmitted in physical transmission lines.
Wireline communication refers to forms of communications where the information is transmitted to the receiver over physical wires, co-axial cables, telephone wires, power lines, or twisted-pair wires. Wireline communication distinguishes itself from other forms of communications such as electromagnetic wireless transmissions or optical signal transmissions.
A wireline communication device can include a transmission path and a reception path. In a transmission path, the data to be communicated is first coded and modulated in a digital domain. The modulated digital data is converted to analog signals in an analog domain by a digital-to-analog converter (DAC). The analog signals are then amplified by a line driver to transmit signals with a large power onto the wired line (or channel). In some systems, further modulation can be implemented on the amplified analog signals after the line-driver.
FIG. 1 shows a conventional wireline transmission circuit 100 for the transmission path of a wireline communication system. The wireline transmission circuit 100 includes a digital domain 107 and an analog domain 108. A digital front-end 101 in the digital domain 107 performs coding and base-band modulation on the digital data to be transmitted. The analog domain 108 includes a D/A Converter 102, a line-driver 103, an optional modulator 104, and a coupling unit 105. The coupling unit 105 can couple the amplified signal from the wireline transmission circuit 100 to a physical line 106 for wireline transmission.
A challenge to the design and implementation of the line-driver is that the line driver is often required to provide large injection power and a small line impedance, to generate a large voltage magnitude, while maintaining excellent linearity in the amplified signals. The large voltage magnitude and large injection power, however, cannot easily be achieved by a system on chip (SOC) solution. A coupling unit 105 having a non-unity magnetic winding ratio is hence used to increase the voltage magnitude of the signals to be transmitted in the physical line 106.
The non-unity magnetic winding ratio in the coupling unit 105 can negatively impact the power efficiency of the line-driver 103. The line-driver 103 is required to provide even smaller impedance and larger current in the amplified signals to achieve the same injected power in the physical line 106.
The state-of-the-art CMOS and semiconductor technologies are driven to achieve greater operation speeds in smaller physical dimensions in integrated circuitry. By reducing the effective gate sizes (width and height), the transistors can operate at greater speeds (greater transconductance) and more transistors can be fit in the same physical space. The scaling down of the transistors also decreases the break-down voltages of the transistors and hence the supply voltages to the integrated circuit have been continuously reduced in deep submicron CMOS technology.
On the other hand, the line-driver in the wireline transmission circuit, as described above, should operate at the largest supply voltage to achieve power efficiency. To overcome the conflicting requirements, foundries commonly use a mixed-oxide CMOS process in which two different oxide thicknesses (dimensions, technology generations) are provided on a single silicon wafer. A deep sub-micron transistor can be placed next to a transistor having larger dimensions, thicker oxide, and thus higher supply voltage on the same silicon substrate. The larger-dimension device is usually used for input and output (I/O) circuits of the chip to sustain high supply voltages and is commonly referred to as an IO device.
There is therefore a need to provide a wireline transmission circuit having improved component integration and smaller device area.